1. Technical Field of the Invention
The present invention relates generally to headlamps for vehicles which include a heat dissipating member for dissipating heat generated by a light source. More particularly, the invention relates to headlamp's for vehicles which employ a light source that has high heat-generating density and is lowered in luminous efficiency and shortened in service life at high temperature.
2. Description of the Related Art
Japanese Patent Application Publication No. 2004-311224 discloses a headlamp for a vehicle which employs LEDs (Light Emitting Diodes) as lighting sources. The headlamp includes a plurality of light emitting units each of which has a projection lens, a reflector and an LED that are sequentially arranged from the front side. The headlamp further includes a heat dissipating member (or support member) that has all of the LEDs of the light emitting units mounted thereon, so as to dissipate heat generated by the LEDs during operation. In addition, the headlamp also includes a housing in which all of the light emitting units are accommodated.
With the above headlamp, however, it may be necessary to arrange a lighting control circuit, which controls the lighting of the LEDs, outside the housing and thus away from the LEDs. Consequently, the electric resistance between the LEDs and the lighting control circuit will be high. Moreover, when a temperature sensing element is arranged in the vicinity of the LEDs for sensing the temperature of the LEDs, it is necessary to electrically connect the temperature sensing element to the lighting control circuit using signal lines that extend through the housing. Consequently, the wiring process of the headlamp will be complicated. Furthermore, to effectively dissipate heat generated by the lighting control circuit, it may be necessary to arrange an additional heat dissipating member for the lighting control circuit outside the housing, thereby increasing both the parts count and size of the headlamp.
Japanese Patent Application Publication No. 2003-68134 discloses a headlamp which includes a discharge bulb as a light source, a lighting control circuit for controlling the lighting of the discharge bulb, a heat dissipating member for dissipating heat generated by the lighting control circuit, and a housing that accommodates therein all of the discharge bulb, the lighting control circuit and the heat dissipating member.
With the above headlamp, it is possible to arrange the lighting control circuit in the vicinity of the discharge bulb. However, to effectively dissipate heat generated by the discharge bulb, it may be necessary to arrange an additional heat dissipating member for the discharge bulb. Consequently, when not properly designed, both the parts count and size of the headlamp will be increased.